The embodiments described herein relate to technology for manufacturing semiconductor devices. In particular, the embodiments relate to an apparatus and method for manufacturing semiconductor devices, capable of removing defocusing effects in photolithography processes.
In fabricating semiconductor devices, a design rule may be reduced by utilizing conditions having increasingly precise control for the photolithography processes involved.
An illumination operation, e.g., an exposure operation to transcribe a specific pattern onto a wafer through a reticle, is regarded as an important step of the photolithography process. There have been many studies of photoresist films and developments of optics and light sources for illumination of the photolithography process. However, as the semiconductor manufacturing process becomes more demanding with a reduced design rule, one needs to improve peripheral techniques as well as the exposure processing technique itself.
One of the peripheral techniques is to regulate roughness on the backside of a wafer. The roughness on the wafer backside usually causes defocusing effects at specific regions, generating process defects. The roughness on the wafer backside is mostly caused by absorption of particles. Namely, the roughness on the wafer backside is considered to be generated from deposition or absorption of particles, which have been caused by prior processing steps such as deposition or etching.
Conventionally, a wet cleaning operation is carried out to lessen such defocusing effects. But the wet cleaning is principally operative to remove particles or pollutants from the front side of the wafer. Recently, single wafer processing equipment is widely used for flexibility corresponding to processing variations and for prevention of particle transcription to the front side of the wafer. Even if the wet cleaning operation is conducted, polluting particles would not be completely removed because of the following consideration: During a standby time from the cleaning step to the photolithography step, these particle pollutants can flow into the photolithography equipment, resulting in an accumulation of pollution. These particles can contaminate a wafer chuck among the photolithography equipment, causing chuck failures and defocusing effects. This obviously harms the photolithography process, degrading productivity and yields.